1. Field of the Invention
The present invention relates to a communications network enabling the connection of a plurality of devices that process data in different formats.
More particularly, the invention is situated in the framework of a home type network.
2. Description of the Prior Art
The modern devices with which a family may be equipped often have to transmit different types of data such as video, sound, photos, text files etc. and the like. The transmission of this data is governed by requirements that are variable depending on the type of data considered. This data must be conveyed especially by means of cables or adapted links. Thus, each data format has a corresponding adapted means of transportation and a type of connector used to connect devices with one another. For example, devices processing digital data may work according to the IEEE-1394 standard.
In order to extend the possibilities of interconnection of devices in a house, there are networks comprising nodes in which interfaces are designed are with different connectors such as, for example, 1394 type connectors, Ethernet type connectors which enable the connection of the corresponding devices. This enables the networking of several devices. However, the connections must be made on one of the nodes of the network or on a hub. The data is then processed independently. There is no provision for conveying several types of data together, on the same transportation means. If the interface comprising several connectors has to be shifted to a wall socket, then it will be necessary to provide as many transportation means, such as cables, as there are different connectors. For cabling in a house, it becomes cumbersome to make several cables go through the walls.
The publication “Home information wiring system using UTP cables for IEEE 1394 and Ethernet systems” in the journal IEEE transactions on Consumer Electronics Vol 47, No. 4, November 2001, describes an adapter which can be used to connect an IEEE1394 cable and an Ethernet cable to an UTP 5 cable comprising four twisted pairs. To do this, the above-mentioned article describes the use of two twisted pairs to obtain the passage of an IEEE1394 signal and two other twisted pairs to obtain the passage of an Ethernet signal.
This publication does not describe the possibility of bringing about the transit, on this same cable, of other data having different formats such as telephone type data.
Furthermore, the transmission of IEEE1394 or Ethernet type data is limited in this case to 100 Mbps. Now, the fact is that use of these protocols in the context of home applications requires far greater transmission capacity, especially for video applications. Furthermore, this distribution of the data requires an equitable sharing of the bandwidth between all the data formats: this is not always so in reality. Indeed, it is sometimes necessary to plan for a bandwidth that is dynamically greater for one type of data as compared with another type of data.
The different types of data that may travel in a home network have variable requirements in order to be transmitted. Thus, the transfer of video type data for example necessitates a particular, continuous bit rate. The same is true for sound. In this case, it is said that the data is isochronous data. On the contrary, for a text file, the data does not need to be transmitted continuously or even regularly. In this case, it is said that the data is asynchronous data. Another example of asynchronous data consists of the commands to turn various apparatuses on or off, and also data intended for printers. A home network must therefore be able to obtain the transit of the asynchronous data as well as isochronous data, this isochronous data having to travel at certain variable speeds and bit rates.
The patent application EP1124357, describes a communications network in which the communications nodes interconnect different IEEE1394 type networks by means of a switched network.
The nodes comprise IEEE1394 type interfaces with a switching unit comprising three input/output ports. They transfer the IEEE1394 packets by one of the input/output ports and send it to another communications node.
The fact is that the configuration of these nodes is not particularly suited to a simple installation in a home environment.
Indeed, the communications nodes as described comprise a plurality of IEEE1355 type connections, and therefore a large number of cables are necessary to provide for the efficient operation of this network.
This large number of cables and connections to be set up makes it difficult to install a network of this kind and above all generates problems of positioning cables and obtaining their passage in a home environment.
Furthermore, the technologies related to the transmission of multimedia information are developing very rapidly, and it is therefore necessary to envisage communications network that can be easily upgraded.
Thus, if new interconnection standards appear, the possessor of such a network will find it necessary to change all the communications nodes even though only one sub-part of these nodes needs to be modified.
The cost associated with this modification therefore entails penalties for the possessor of this network.